ML12110A175
| ML12110A175 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 04/18/2012 |
| From: | Gillespie T Duke Energy Carolinas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML12110A175 (7) | |
Text
Duke T.
PRESTON GILLESPIE, JR.
7Energy Vice President Oconee Nuclear Station Duke Energy ONOI VP / 7800 Rochester Hwy.
10 CFR 50.90 Seneca, SC 29672 864-873-4478 864-873-4208 fax T. Gillespie@duke-energy. com April 18, 2012 Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001
Subject:
Duke Energy Carolinas, LLC Oconee Nuclear Station, Units 1, 2, and 3 Docket Numbers 50-269, 50-270, and 50-287, Renewed Operating Licenses DPR-38, DPR-47, and DPR-55 Tornado and High Energy Line Break Mitigation License Amendment Requests -
Revised Response to Request for Additional Information for Item No. 99
Reference:
- 1. Letter from T. Preston Gillespie, Vice President, Oconee Nuclear Station, Duke Energy Carolinas, LLC, to the U.S. Nuclear Regulatory Commission, "Tornado and High Energy Line Break (HELB) Mitigation License Amendment Requests (LARs) - Responses to Request for Additional Information," dated December 16, 2011.
By letter dated December 16, 2011, Duke Energy Carolinas, LLC (Duke Energy) responded to a Nuclear Regulatory Commission (NRC) Request for Additional Information (RAI) (Reference 1). On March 26, 2012, following a conference call between Duke Energy and the Staff, additional clarification was requested to be added to the previous RAI 99 response. The submrittal contains Duke Energy's revised response to that RAI.
If you have any questions in regard to this letter, please contact Stephen C. Newman, Regulatory Compliance Senior Engineer, Oconee Nuclear Station, at (864) 873-4388.
I declare under penalty of perjury that the foregoing is true and correct. Executed on April 18, 2012.
Sincerely, T. Preston Gillespie, Jr.
Vice President Oconee Nuclear Station Enclosure m oo www. duke-energy. corn
Nuclear Regulatory Commission Revised Response to Request for Additional Information Item No. 99 April 18, 2012 Page 2 cc: (w/enclosure/attachments)
Mr. John P. Boska, Project Manager U. S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation 11555 Rockville Pike Rockville, MD 20852 Mr. Victor M. McCree, Administrator, Region II U.S. Nuclear Regulatory Commission Marquis One Tower 245 Peachtree Center Ave., NE, Suite 1200 Atlanta, GA 30303-1257 Mr. Andrew T. Sabisch NRC Senior Resident Inspector Oconee Nuclear Station Ms. Susan E. Jenkins, Manager Radioactive & Infectious Waste Management SC Dept. of Health and Environmental Control 2600 Bull St.
Columbia, SC 29201
Enclosure Duke Energy Revised Response to RAI item No. 99
Enclosure - Revised Response to RAI Item No. 99 April 18, 2012 Page 2
RAI 99
By letter dated October 8, 2010, the NRC issued RAI 1 [H]. The licensee responded to the RAI by letter dated December 7, 2010. The licensee's response to the RAI provides atmospheric dispersion factors (X/Q values) used in the dose assessment for postulated HELBs in the letdown line.
Please provide a reference which documents the establishment of these control room (CR) X/Q values as licensing basis values for the HELB dose assessment.
Please clarify whether the CR X/Q values shown on page 4 would apply to the worst-case main steam line break following a tornado.
Provide a reference to any other CR x/Q values associated with design basis accidents that may result from the occurrence of a tornado.
Duke Energy Response:
The control room (CR) X/Q values used for the HELB letdown line break event dose analysis are calculated based on the same methodology that the NRC approved for the Alternative Source Term (AST) License Amendment Request (LAR). As shown in the table below, the x/Q associated with an ADV release point was used for the HELB letdown line break, since it is conservative relative to the HELB letdown line break release location, by this comparison of the distances, directions, and elevations relative to the as-built locations of the control room intakes (which are at an elevation 26.6 meters above plant grade):
Distance from CR Intake (meters)
Direction from CR Intake (degrees)
Elevation above plant grade (meters)
HELB Letdown Line Break Release 51.1 268 7.8 Location ADV Release 52.2 262 13.0 Location The resulting x/Qs, unadjusted for flow imbalance between intakes, are:
HELB Letdown Line Break Release ADV Release Location Location x/Q X/Q 0-2 Hours 1.75E-03 1.79E-03 2-8 Hours 1.17E-03 1.25E-03 8-24 Hours 5.11 E-04 5.45E-04 24-96 Hours 3.81E-04 4.17E-04 Hours96-720 3.24E-04 3.34E-04 Hours
Enclosure - Revised Response to RAI Item No. 99 April 18, 2012 Page 3 Bounding x/Qs for Oconee release points (including the ADV) were previously submitted to the NRC with the AST LAR on October 16, 2001. Duke Energy received the NRC Safety Evaluation approving full-scope AST implementation for Oconee on June 1, 2004. The most current calculated x/Q values vary slightly from those initially submitted in the October 2001 AST LAR, based on final as-built locations of Duke Energy's dual control room intakes installed in 2005. The as-built X/Q values are reflected in current UFSAR Table 15-61 (shown below).
Note that the UFSAR values do not reflect the adjustment for the airflow split between the dual intakes reflected in the x/Qs used in the HELB letdown line break dose analysis.
The analysis of a worst-case main steam line break following a tornado will credit steam line isolation by the Main Steam Isolation Valves (MSIVs), which will be located upstream of the current location of the Main Steam Safety Valves (MSSVs) and further from the control room intakes than the current MSSVs. Thus, the release location is expected to be less limiting than the MSSV X/Qs shown in UFSAR Table 15-61.
The x/Q values from UFSAR Table 15-61, adjusted as necessary for the airflow imbalance between the dual intakes, are used for design basis accidents at Oconee. Duke Energy is not requesting approval for any new CR x/Q values for accidents that may result from the occurrence of a tornado.
Enclosure - Revised Response to RAI Item No. 99 April 18, 2012 Page 4 Oconee Nuclear Station TJFAR Table 161l (Page 1 of 2)
Table 15-61. Control Room Atmospheric Dispersion Factors (7fQs)
Release Type Bounding y/Q (sedm*)
Units Vet Releases 0 to 2 hr 9A43E-04 2 to 8 h 6-00E-04 8 to 24 hr 2.41E-04 i to 4 dav.
1-87E-04 4 to 30 days 1I.4E-04 Main Steam Penetration Releases 0 to 2 hr
.76E-04 2 to 8 hr 4-09E-04 8 to 2-4 hr 1.72E-04 1 to 4 days 1-34E-04 4 to 30 days 1 08E-04 Equipment Hatch Reteases 0 to 2 hr 6.59E-04 2 to, hr 4.-6E-04 S to 2,4 hr 2-13E-04 1 to 4 days 1.65E-04 4 to 30 days 1.28E-04 ADV Releases 0 to 2 hr 1-79E-03 2 to 8 hr 1-25E-03 8 to 24 hr 5-45E-04 1 to 4 days 4.17E-04 4 to 30 days 3-34E-04 MSSV Releases 0 to 2 hr 1.91E-03 2 to S hr 1.33E-03 8 to 24 hr 5.S6E-04 i to 4 das 4-52E-04 4 to 30 days 3-54E-04 (31 DEC 2009)
Enclosure - Revised Response to RAI Item No. 99 April 18, 2012 Page 5 Oumnee NdVv r St a ion tT&.R Tahle 1.9-61~ag (PV fZ o to 21 b.
2 to S hy Sto 24hr 4 to r, 2tSh Sto 24 h 4to3d BXVSTR~
Q to 2 hr 2 to' 8 hr 8 to 24 4 rc z-i:-
Boiwdiug i!Q (st in 121E 3 S39E-04 33O~-O4 2~S1E-O4 2~E 4 3LE 4 L E 4 LO4E 4
~S9E~O5 610E-05 4~76E-O4
~7E-O4 13 E 4 1.0 E 4
.99E 5 (31 DEC :009)